Fuse block



Jan. 24, 1939. CQRBETT 2,145,154

FUSE BLOCK Original Filed March 22, 1955 3 Sheets-Sheet 1- INVENTOR4621M g ymwm Jan. 24,1939. CORBETT 2,145,154

FUSE BLOCK Original Filed March 22, 1935 3 iset' 2 Patented Jan. 24,1939 UNITED STATES PATENT OFFICE FUSE BLOCK Delaware Application March22, 1935, Serial No. 12,426 Renewed April 2, 1938 12 Claims.

This invention relates to a fuse block, or more properly to a compositeassembly comprising :all the essential elements of a fuse blockuti-lizable as such, or in building up assemblies such as panel boards.

An object of the invention is to provide a fuse mounting assembly,performing the functions of a fuse block, in which contact-carryingframes are readily mountable on and demountable from the bus bars, tomake firm and adequate contact between the contact elements carried byindividual frames and the bus :bars to which the icontact-carryingframes are mounted.

Another object of the invention is to provide y a fuse block assembly inwhich the required quantity of insulation is minimized by the form andarrangement of the insulating elements, constituting a base structureupon which the bus bars are mounted; and to provide an assembly in whichthe several insulating elements of the base structure are of suchstructural simplicity as to minimize molding operations requisite intheir production.

Another object of the invention is to provide in combination a basestructure, and one or more individual contact-carrying frames formounting on the base structure, so arranged that the base structure isdiscontinuous in the regions in which contacts carried by the framesmounted to the base make contact with the bus bars, and such arrangementof contact-carrying frames and contacts thereon that the fuse contactstructures on the frames are unhoused, and are subjected to aircirculation therearound; thus utilizing as an insulating medium airwhich serves also to prevent overheating in the fuse contacts and fuses,thus preserving a true rating of the fuses.

A further object of the invention is to provide contact frames readilyand separately mountable on and demountable from a base structure, eachof said frames carrying contacts for fuses of different rating adaptedto the several circuits in which the fuses are to be associated, thecontact-carrying frames severally comprising contacts, each adapted toreceive fuses appropriate to the circuit in which the contacts areconnected.

A further object of the invention is to provide an assembly of thenature above indicated, mountable and demountable contact-carryingframes, each comprising a deck having the circuit contacts arranged andmounted on the upper face of the deck with the center contacts of thefuse contact assembly extending beneath the deck and upwardly beyond theupper face of the deck into cooperative association with the circuitcontacts carried thereon; thus minimizing possibility of short-circuitduring mounting and demounting of the contact-carrying frames.

A still further object of the invention is to provide a contact-carryingframe, as immediately above described, in which means are so mounted inrelation to the fuse contacts that the center contact of the assembly isscreened from electrical contact with any conductive instrument, save afuse suitably constructed to establish connection with the centercontact of the assembly.

In fuse blocks as made up for mounting in fuse boxes, and in panelboards and the like, it is generally desirable that the fuse block beformed of a plurality of separable elements, since such unitconstruction facilitates wired installation of the fuse block, andfacilitates changes in wiring. Also such division into separableelements permits an open construction, utilizing air as an insulatingand cooling medium in the manner noted as an object of my presentinvention. It further is advantageous that an element of the fuse blockmay be removed or replaced without disturbing the position, orinterrupting the electrical connection, of other separable elements ofthe fuse block.

Since fuse boxes and panel boards usually are arranged to provide asafety factor in a plurality of circuits capable of carryingcurrent ofdifferent amperage,- the fuse block necessarily comprises contacts forfuses constructed to tolerate a variety of amperages. If then, a fuseblock is to be so made up that the several contact structures comprisedthereby are made compatible, by

contouring or otherwise, only with fuses so limited in capacity that anappropriate safety factor is provided in each circuit, it becomes highlyadvantageous to provide an arrangement in which a plurality of separablefuse-carrying elements are individually mountable and demountable tomake or break contact with the bus bars of the fuse block assembly.

It is highly desirable that the fuse contacts of a contact blockcomprise structures for preventing tampering with the fuse contacts.That is, it is highly desirable that means should be provided to preventestablishment of a circuit at a fuse contact in the absence of anoperable fuse in the circuit. It frequently happens that, a fuse havingblown, a person deriving current at the fuse box will, either ignorantlyor recklessly, establish a substantially infusible connection at thebase of the fuse contact socket, thus depriving the circuit of theprotection provided by the ill) grooved longitudinally outward from thesocket I to provide a channel 1a for receiving a contact bar 8,connecting the socket with a binding post 3. Desirably, each of thecontact-carrying frames has thereon vertical posts H), which support aninsulating cover 1! perforated in the regions I 2, to give access to theshells, or sockets, l.

Contact between sockets I and bus bars 2 is provided by center contacts,which serve, additionally, firmly to position each contact-carryingframe on the base assembly. Each center contact comprises a screw l3,the .head of which projects above the upper surface of deck 6, withinits associated shell socket 1. Each of the screws l3 also makeselectrical contact with, and secures to the under side of the deck 6., aU- shaped contact element [4, which has one leg engaged by the screw l3and lying against the under face of the deck of the contact-carryingstructure, the other leg of the U forming a blade for engagement withjaw contact l5. Jaw contact l5 comprises, as is shown, a base, and twojaws which extend horizontally outward from the base, and are broughtinto a position of close parallelism to each other, to receive andengage the blade Me of contact element l4. Jaw contacts #5 are held inclose and firm contact with a side face of each of the bus bars 2 bymeans of mounting screws I6.

In assembly of a fuse block comprising the elements described, thecontact-carrying frames are placed one at a time in the channels formedby the shoulders 50 of the two base elements I, with the contact bladeMa of element I4 in alignment with the jaws l5a and [5b. In thisposition a contact-carrying frame lies to the left of the positionillustrated in Figs. I and II, and, by moving the contact element to theright, it is brought into the position shown in Figs. I and II; in whichposition the blades Ma are closely and firmly engaged by the contactjaws, to make connection of each center contact with one of the busbars, and to firmly position the contact-carrying frame on the baseassembly.

It will be observed that each of the contactcarrying frames may beremoved from its mounted position, making contact with the two bus bars,simply by moving the frame to the left from the position shown in Figs.I and II, and lifting it from the base assembly. Obviously, this may bedone without disturbing the mounting of any other contact-carrying frameof the fuse block either physically or electrically.

In the modified assembly shown in Figs. III to VI, inclusive, of thedrawings, the bus bar supports, or base elements, are ties of a formstill simpler than the form of those shown in Figs. I and II. These tiesI! are mere rectangular and elongate blocks of insulating material,which are secured by screws l8 to an underlying structure, such as theinner wall of a fuse box. The bus bars l9 lie upon these blocks, inbridging relation to the tie block assembly, and are secured to the tieblocks by screws 20. It will be noticed that the blocks I! and the busbars 19 define, by their arrangement, spaces 2| of rectangularconfiguration. As will be explained, these spaces 2| are useful inpositioning the contact carrying frames, and in positively preventingshifting of the contact-carrying frames when mounted.

In this modification, the contact-carrying frames comprise each a deck22, from which depends a. seating boss 23, which is of rectangularcross-section, fitting the rectangular spaces 2| defined by the ties l1and bus bars l9. Upstanding from the deck 22 is a center post 24, whichoverlies the seating boss 23, and which has a bore 24a extendinglongitudinally therethrough. Posts 25, for supporting an insulatingcanopy or cover 26, also extend upwardly from deck 22. The entirestructure of deck, mounting boss, center post, and cover-supportingposts is desirably made, as shown, of a single block of moldedinsulating material.

1 In Figs. III and IV, the frame is shown as carrying two screw shellsockets 2'! which are electrically connected with binding posts 28, bymeans of strips, or bars, 29 of conducting material. At the base of eachshell socket 2'! lies the head of a contact screw 30, the shank of whichprojects through the deck. Terminally, the shank of screw 30 carries acontact nut, or threaded washer, 3|, to provide a relatively extendedcontact area.

In mounting the contact frames on the base structure, the frame assemblyis brought into position with its seating bosses 23 extending into thespaces 2l of the base assembly, and with the contact nuts 3| contactingthe upper surfaces of bus bars i9. In order, however, that the framesmay be firmly mounted on the base assembly, and that close electricalcontact with the bus bars may be continuously maintained, means areprovided for forcing the contact-carrying frame toward the baseassembly, and for firmly engaging it thereto.

The positive engaging means of the assembly comprises an elongate screw32, which is headed upwardly of center post 24, and the threaded shankof which, passing through the bore of the center post and downwardlybeyond seating bosses 23, enters a threaded socket 33.

When any contact-carrying frame has been positioned on the baseassembly, it is positively engaged by passing its associated centerscrew 32 through the center post and into the socket 33 which is inalignment with the bore through the center post. By tightening down onits associated screw 32, each contact-carrying frame is therefore drawnpositively to the base assembly, and the contact nuts 3| of the frameare pressed firmly and positively into contact with bus bars l9. lhecontact-carrying frame is freed, for removal from mounted position,merely by releasing screw 32 from its engaging socket 33.

It will be observed in connection with both modifications of myapparatus that the positive mounting of a contact-carrying frame on thebase assembly also makes, and maintains, good electrical connectionbetween bus bars of the assembly and contact structures carried by theframe.

In each of the modifications shown and decribed, the contact-carryingunit is a frame carrying two contact structures for the connection offuses. It will be understood that the structure of either form ofcontact-carrying frame may readily be so modified that each framecarries but a single contact structure; or, if desired, each unit mayconsist of a frame carrying more than two contact structures.

Referring to Fig. VIII of the drawings, a selective contact-making, andselective fuse-receiving, structure is shown as associated with acontact structure mounted on the deck 6 of a contactcarrying frame, madein accordance with the showing of Figs. I, II, and VII. This addedstructure comprises a barrel 34 of insulating material, having acentrally disposed bore 35 therethrough.

The lower region 35a of bore 35 -is constricted, and an annular rib 31projects into the bore between the upper region thereof and the lowerconstricted region thereof. Traversable in bore 35 is a plunger 38 ofconductive material, having at the upper extremity thereof an integralcollar 38a, and at the lower extremity thereof a washer 38b riveted, orotherwise suitably secured, to the lower terminal of the plunger. A coilspring 39 lie in the main portion of bore 35, surrounding plunger 38 andbearing respectively against collar 38a and the annular inwardlyextending rib 31. This coil spring 39 exerts a constant force tending tomaintain plunger 35 in its uppermost position, with collar 35?) abuttingthe under face of rib 31, and spaced a substantial distance from thehead of screw [3.

It will be apparent that this structure, inserted within screw shell 1,screens contact screw it from contact in the region thereof whichprojects above the deck 5. In order, therefore, that electricalcommunication be established between a bus bar engaged by the bus barcontact structure and the screw shell I, it is necessary that conductiveplunger 38 be forced downwardly against the resistance of coil spring 39into a position abutting contact screw [3, and that a conductor bemaintained between it and the screw shell. In inoperative condition ofthe contact structure, therefore, the bus bar contact is screened fromdirect contact with a conductor. This arrangement prevents theestablishment of electrical communication between the bus bar contactand the screw shell, in the absence of a fuse, and thus preventsestablishment of a circuit which lacks the protection afforded by afuse. Also, as applied to the mountable and demountable contact frame,it prevents the establishment of an accidental short, in the absence ofa fuse, and in mounting, or demounting, the contact-carrying frame fromthe base structure upon which it is mountable. This provides a safetyfactor, rendering it safe to mount the contact-carrying frames, withoutdeenergizing the bus bar.

A form of fuse 4D, suitable for use in conjunction with thefuse-receiving contact structure is shown in position to be insertedinto the screw shell 7. It will be noted that the fuse 41! comprises anelongate terminal 4!, which is surrounded by a skirt 62, carrying athreaded, conductive, terminal element '13 adapted to make contact withscrew shell I.

When fuse 59 is screwed into the contact shell, as shown with relationto the contact shell 27 of Fig. IX, skirt d2 enters the annular region 3lying between the exterior surface of barrel 3::- and the interiorsurface of the screw shell. -As the fuse is screwed into position,terminal 4!, bearing against conductive plunger 38, forces the plungerdownwardly in bore 35;. Terminal 1! is of such length that, before thelimit of move ment of fuse 4G in the screw shell has been reached,conductive plunger 38 is brought into contact with the upper face of thehead of screw it. This establishes electrical communication between thebus bar contact and the screw socket, through the fuse.

In order that fuses of predetermined capacity may be associated onlywith contact structures which in turn are associated with circuits of nolesser electrical capacity, the thickness of barrel 34 of the selectivecontact-making structure, and the thickness of fuse skirt 52, may bemutually apportioned. Thus, the contact structure, or structures, on anindividual contact-carrying frame are arranged to provide an annularspace M of a width apportioned to the skirt width of fuses to beassociated on the contact-carrying frame. By'making the skirt 42, of thefuses of greatest capacity, of the greatest thickness, and byprogressively decreasing the thickness of this skirt within decreasedcapacity of the fuse, assurance may be had that a fuse of capacity toogreat for that of the circuit in which it is to be incorporated cannotbe associated with the contact-carrying frame for that circuit.

As above noted, the use of separately mountable and demountable contactframes gives a highly desirable accommodation to selectivity in thecapacity of the fuse, or fuses, associated with the frames. Change inthe capacity of any individual circuit, safeguarded by my fractionatedfuse block assembly, can thus be readily accommodated by removal of acontact-carrying frame with contacts inappropriate to the changedcircuit, and by the mounting of substituted frame-carrying contacts andfuses appropriate to the changed circuit. This may be done, and donesafely, without deenergizing the bus bars, or interfering with theactive condition of other circuits safeguarded by connectioncontact-carrying frames.

There are other modes of rendering difficult the use of an overecapacityfuse in a contact structure on the contact-carrying frame. For example,the diameter of the bore 35 in barrel 34 of the contact screening insertmay be made too smallto receive the terminal 4! of any fuses save thoseof adequately low capacity. Also the length of conductive plunger as,with respect to the effective seated length of fuse terminal at, may bevaried in accordance with corresponding variation in the length of thefuse terminal. A combination of these two limiting factors may beemployed.

I claim as my invention:

with 7 other 1. In a fuse block assembly the combination of a basestructure comprising spaced bars of insulating material secured to anunderlying wall and a bus bar bridging between said insulating bars,with a contact-carrying frame comprising a deck, a bus bar contactextending beneath the deck in position to make direct electrical contactwith the said bus bar, and means for mounting the contact-carrying frameon the base structure with the bus bar contact thereon in electricalcommunication with the bus bar in an interval between insulating bars ofthe base structure.

1 2. In a fuse block assembly the combination of a base structurecomprising spaced bars of insulating material secured to an underlyingwall and a bus bar bridging between said insulating bars, with acontact-carrying frame comprising a deck, a bus bar contact extendingabove the deck and extending beneath the deck in position to be broughtinto direct electrical communication with the said bus bar, means formounting the contact-carrying frame on the base structure with the busbar contact thereon in direct electrical communication with the bus barin an interval between insulating bars of the base structure,v a circuitcontact carried at the upper side of the deck in spaced relation to saidbus bar contact, said bus bar contact and said circuit contact beingarranged to be bridged by a fuse, and selective contact-making meansassociated with the contact structure carried by the said selectivecontact-making means bein arranged normally to screen the upwardextension of the bus bar contact from the establishment of electricalcommunication therewith and being operable by a fuse to establishelectrical connection between the fuse and said bus bar contact.

3. In a fuse block assembly the combination with an underlyingsupporting wall of a structure comprising spaced bars of insulatingmaterial secured to said underlying wall bus bar bridging between saidinsulating bars, a contact-carrying frame comprising a deck having apositioning boss adapted to lie between adjacent insulating bars of thebase assembly, a bus bar contact extending beneath the said deck inposition to make direct electrical contact with the said busbar in aninterval between insulating bars, and a member adapted to pass throughthe positioning boss of the contact-carrying frame and regulably toengage in said underlying sup-- porting wall thereby to force thecontact-carrying frame to said base structure and to force the contactelement carried thereby into electrical contact with said bus bar.

4. In a fuse block assembly the combination with anunderlying supportingwall of a structure, comprising spaced bars of insulation secured tosaid underlying wall and a bus bar bridging between said insulatingbars, a contactcarrying frame comprising a deck having a positioningboss adapted to lie between adjacent insulating bars of the assembly, abus bar contact extending above said deck and extending beneath the saiddeck in position to make direct electrical contact with the bus bar inan interval between insulating bars, a circuit contact carried at the 1upper side of the deck in spaced relation to upward extension of saidbus bar contact, said bus bar contact and said circuit contact beingarranged to be bridged by a fuse, selective contactmaking meansassociated with said bus bar contact, said selective contact-makingmeans being arranged normally to screen the upward extension of said busbar contact from the establishment of electrical communication with thebus bar therethrough and being operable by a fuse to establishelectrical communication from the bus bar by way of the bus bar contactand the fuse to the circuit contact, and a member adapted to passthrough the positioning boss of the contact-carrying frame and regulablyto engage in said underlying structure thereby to force thecontact-carrying frame to said base structure and to force the bus barcontact carried thereby into electrical contact with said bus bar.

5. In a fuse block assembly the combination with an underlying wall of abase structure comprising spaced bars of insulating material secured tosaid underlying wall and a bus bar bridging between said insulatingbars, a contact-carrying frame arranged to rest upon said insulatingbars and carrying a depending contact positioned to make electricalcontact with said bus bar in an interval between insulating bars inmounted positioning of the contact-carrying frame thereon, and anengaging member mounted in the contactcarrying frame and adapted toengage in said underlying wall, thereby to hold the contactcarryingframe to said base structure and to hold the contact element dependingtherefrom in electrical contact with said bus bar.

6-. In a fuse block assembly the combination a base structure comprisingspaced bars of insulating material secured to an underlying wall and abus bar bridging between said insulating bars, with a contact-carryingframe comprising a deck, a bus bar contact extending above the deck andextending beneath the deck in position be brought into direct electricalcommunica tion with the said bus bar, means for mounting thecontact-carrying frame on the base structure with the bus bar contactthereon in electrical communication with the bus bar in an intervalbetween insulating bars of the base structure, a screw shell forming anelement of the contact structure carried by the frame and surroundingthe upward extension of said bus bar contact, and means in said shelladapted to limit the space therewithin and thereby to limit thereceptivity of the shell to fuses formed in accordance with the spacelimitation within the shell effected by said space limiting means.

7. In a fuse block assembly the combination of a base structurecomprising an insulating base and a bus bar mounted thereon, acontact-carrying frame comprising an insulating deck, a contact assemblycomprising contact elements mounted on the upper surface of the deck andarranged to be bridged by a fuse lying wholly at the upper face of thedeck, means projected through the deck arranged to maintain the saiddeckcarried contact assembly in electrical connection with the said busbar, and an insulating canopy mounted on the deck and spaced from theupper surface of the deck, said insulating canopy being perforate in aregion overlying the said contact assembly.

8. In a fuse block assembly the combination of a base structurecomprising an underlying base and a bus bar mounted on said base ininsulated relation thereto, with a contact-carrying frame comprising adeck, a bus bar contact extended above the deck and extended beneath thedeckin position to make electrical contact with the bus bar, aconnecting member projected beneath the deck in a position of electricalseparation from the bus bar contact and adapted by engaging theunderlying base to hold the downward extension of the bus bar contact inelectrical contact with the bus bar, a circuit contact carried at theupper side of the deck in spaced relation to the upward extension of thebus bar contact, said bus bar contact and said circuit contact beingarranged to be bridged by a fuse, and selective contact-making meansassociated with said bus bar contact, said selective contact-makingmeans being arranged normally to screen the upward extension of said busbar from the establishment of electrical communication with the bus bartherethrough and being operable by a fuse to establish electricalcommunication from the bus bar by way of the bus bar contact and thefuse to the circuit contact.

9. In a fuse block assembly the combination of a base structurecomprising an underlying base and a bus bar mounted on said base ininsulated relation thereto, with a contact-carrying frame comprising adeck, a bus bar contact extended above the deck and extended beneath thedeck in position to make electrical contact with the bus bar, a mountingscrew passed through the deck in electrical separation from the bus barcontact and having a threaded engagement with the underlying basethereby to force the bus bar contact extended beneath the deck intoelectrical contact with the bus bar, a circuit contact carried at theupper side of the deck in spaced relation to the upward extension of thebus bar contact, said bus bar contact and said circuit contact beingarranged to be bridged by a fuse, and selective contact-making meansassociated with said bus bar contact, said selective contactmaking meansbeing arranged normally to screen the upward extension of said bus barfrom the establishment of electrical communication with the bus bartherethrough and being operable by a fuse to establish electricalcommunication from the bus bar by way of the bus bar contact and thefuse to the circuit contact.

10. In a fuse plug assembly the combination of a base structurecomprising an underlying base and a bus bar mounted on said base ininsulated relation thereto, with a contact-carrying frame comprising adeck, a bus bar contact extended above the deck and extended beneath thedeck in position to make electrical contact with the bus bar, aconnecting member projected beneath the deck in a position of electricalseparation from the bus bar contact and adapted by engaging theunderlying base to hold the downward extension of the bus bar contact inelectrical contact with the bus bar, a circuit contact mounted at theupper side of the deck in spaced relation to the upward extension of thebus bar contact, said bus bar contact and said circuit contact beingarranged to be bridged by a fuse, and selective contact screening meansassociated with said bus bar contact at the upper side of the deck andarranged to limit conductive agencies effective to establish electricalcommunication between the circuit contact and the bus bar contact to afuse selectively adapted to said contact screening means 11. In a fuseblock assembly the combination of a base structure comprising anunderlying base and a bus bar mounted on said base in insulated relationthereto, with a contact-carrying frame comprising a deck, a bus barcontact extended above the deck and extended beneath the deck inposition to make electrical contact with the bus bar, a mounting screwpassed through the deck in electrical separation from the bus barcontact and having a threaded engagement with the underlying basethereby to force the bus bar contact extended beneath the deck intoelectrical contact with the bus bar, a circuit contact carried at theupper side of the deck in spaced relation to the upward extension of thebus bar contact, said bus bar contact and said circuit contact beingarranged to be bridged by a fuse, and selective contact screening meansassociated with said bus bar contact at the upper side of the deck andarranged to limit agencies effective to establish electricalcommunication between the circuit contact and the bus bar contact to afuse selectively adapted to said contact screening means.

12. In a fuse plug assemblythe combination of a base structurecomprising an underlying base and a bus bar mounted on said base ininsulated relation thereto with a contact-carrying frame comprising adeck, a bus bar contact extended above the deck and extended beneath thedeck in position to make electrical contact with the bus bar, and amounting screw passed through the deck and projected therebeneath in aposition of electrical separation from the bus bar contact and havingthreaded engagement with the underlying base, said mounting screw by itsengagement with the underlying base exerting a regulable force tomaintain electrical contact between the bus bar contact and the bus barby forcing the bus bar contact against the bus bar.

ALFRED CORBE'IT.

